全新java初学者实践教程6(Java SE5.0版)
Dc2H<=]; 基本语法3
]@0C1r )1N~-VuT Dr)B0]KG 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
',P$m&z OQ&l/|{O0? [font="Times] 1.循环语句[font="Times]:while,do-while,for
0.+MlyA G
.NGS%v [font="Times]2.分支语句[font="Times]:if-else,switch,
ZwM(H[iqL [font="Times]
-e(e;e 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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Zcjh 4.异常处理语句[font="Times]:try-catch-finally,throw
!cW6dc^ .k cyw>T`I 实践:
e w?4; [font="Times] 1.循环语句
"Doz~R\\ [font="Times] while 语句
1R-WJph [font="Times]class While {
&.F]-1RN[ [font="Times]public static void main(String args[]) {
f}=>c|Do [font="Times]int n = 10;
H}?"2jF [font="Times]while(n > 0) {
Zjd9@ [font="Times]System.out.println("tick " + n);
R.(PZC vS [font="Times]n--;
Qco8m4n [font="Times]}
fN&@y$ [font="Times]}
;Nk,bb K [font="Times]}
|0OY>5 [font="Times] do…while 语句
HAwdu1$8 [font="Times] class DoWhile {
5X&Y~w,poU [font="Times]public static void main(String args[]) {
Ym% XCl [font="Times]int n = 10;
TXdo,DPv7 [font="Times]do {
{.eo?dQ [font="Times]System.out.println("tick " + n);
{^8?fJ/L [font="Times]n--;
rny(8z%Ck- [font="Times]} while(n > 0);
s5h}MXIXw [font="Times]}
Np7+g`nG [font="Times]}
tTOBKA89 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
pmRm&VgE. [font="Times] for语句
f YSH]! [font="Times] class ForTick {
galzk $D [font="Times]public static void main(String args[]) {
LY-,cXm&| [font="Times]int n;
zG{P5@:.R [font="Times]for(n=10; n>0; n--)
9A~w2z\G [font="Times]System.out.println("tick " + n);
rtNYX=P [font="Times]}
iYD5~pK8 [font="Times]}
e.\dqt~%y 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
<p/zm}?') 还有啊,[font="Times]for循环的部分可以为空的
DG?g~{Y~b [font="Times]class ForVar {
-U*J5Q [font="Times]public static void main(String args[]) {
Qo32oT[DM [font="Times]int i;
,BUrZA2\U$ [font="Times]boolean done = false;
;.'?(iEB [font="Times]i = 0;
ulE5lG0c [font="Times]for( ; !done; ) {
X!_&%^L' [font="Times]System.out.println("i is " + i);
PriLV4? [font="Times]if(i == 10) done = true;
@Bds0t [font="Times]i++;
4M#i_.`z [font="Times]}
h+=IxF4 [font="Times]}
":0u%E?s [font="Times]}
循环语句的例子下载 By waD? [font="Times] 2.分支语句[font="Times]
%_."JT$v{ [font="Times] if/else语句
v*[UG^+) [font="Times]class IfElse {
eAmI~oku [font="Times]public static void main(String args[]) {
_K}q%In [font="Times]int month = 4; // April
s]]lB018O\ [font="Times]String season;
fV@[S [font="Times]if(month == 12 || month == 1 || month == 2)
~UJ.A<>Fh [font="Times]season = "Winter";
HjIIhl?UY [font="Times]else if(month == 3 || month == 4 || month == 5)
,OWk[0/ [font="Times]season = "Spring";
UB/"&I uo [font="Times]else if(month == 6 || month == 7 || month == 8)
h4jo<yp\ [font="Times]season = "Summer";
.fbY2b([ [font="Times]else if(month == 9 || month == 10 || month == 11)
?5FlbiT [font="Times]season = "Autumn";
!B 4z U:d [font="Times]else
9u^M{6 [font="Times]season = "Bogus Month";
)X?oBNsj [font="Times]System.out.println("April is in the " + season + ".");
FRuPv6 [font="Times]}
f"RC(("6W [font="Times]}
yX4Vv{g [font="Times]//这段程序输出[font="Times]:
/5)*epF+ [font="Times]//April is in the Spring.
ugN t7P,^ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
|QS3nX< [font="Times] switch语句
eZEk$W% [font="Times] class Switch {
fX]`vjM{ [font="Times]public static void main(String args[]) {
r1}^\C [font="Times]int month = 4;
SV@*[r [font="Times]String season;
<l(n)|H1P [font="Times]switch (month) {
MA,*$BgZ [font="Times]case 12:
ltfKqY- [font="Times]case 1:
<3!Al,!ej@ [font="Times]case 2:
)by7[I0v [font="Times]season = "Winter";
Tf~eH!~0 [font="Times]break;
yUj`vu2 [font="Times]case 3:
o3V\ [font="Times]case 4:
UAPd["`)y [font="Times]case 5:
Lo3N)~5 [font="Times]season = "Spring";
/cb`%"Z [font="Times]break;
$m;`O_-T [font="Times]case 6:
y{/7z}d [font="Times]case 7:
'y\Je7 [font="Times]case 8:
?HJh;96B [font="Times]season = "Summer";
+l^tT&s;f [font="Times]break;
5CZyA`3V^5 [font="Times]case 9:
vP x/&x [font="Times]case 10:
~v%6*9 [font="Times]case 11:
?V,q&=9 [font="Times]season = "Autumn";
uLafO=Q [font="Times]break;
w%.hALN5-C [font="Times]default:
(IBT|K [font="Times]season = "Bogus Month";
XjF@kQeM= [font="Times]}
dpTsTU!\ [font="Times]System.out.println("April is in the " + season + ".");
arDl2T,igF [font="Times]}
g!R7CRt% [font="Times]}
分支语句代码下载 H,]8[qT< n1J u=C [font="Times]switch语句适合于条件非常多的逻辑
kh9'W<tE 请看上述语句可以混合使用,请看
下载例子